Rock-cutting apparatus



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APPLICATION FILED SEPT. 13. 1913.

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ROBERT TEMPLE, OF DENVER, COLORADO, ASSIGNOR TO IMPERIAL TUNNELLING MACHINE COMPANY, A CORPORATION OF ARIZONA.

ROCK-CUTTING APPARATUS.

Application filed September 13, 1913.

T 0 all whom it may concern Be it known that 1, ROBERT TEMPLE, a citizen of the United States, residing at Denver, in the county of Denver and State of Colorado, have invented certain new and useful Improvements in Rock-Cutting Apparatus, of which the following is a specification. I

The object of my invention is to provide efficient rock cutting means. I describe and illustrate herein a tunneling machine, that is a machine adapted to advance through rock in a horizontal or a substantially horizontal plane, but many of the features of my invention are applicable to use in sinking shafts and many of the details of my invention will also find utility in still other connections. While the apparatus herein described and illustrated is at the present time the preferred embodiment of my invention, the invention can be embodied in many mechanically difi'erent forms of mechanism and is not limited to the precise construction herein made the basis of explanation.

In the drawings Figure 1 is a side elevation of the ent1re machine.

Fig. 2 is a plan view of the same, both Figs. 1 and 2 being broken away at the central part to indicate that the apparatus as an entirety may be of greater or less length as found expedient and desirable.

Fig. 3 is a front elevation of the apparatus.

Fig. 4 is a front elevation similar to Fig. 3, certain parts beingshown in section.

' Fig. 5 is a plan view of the forward part of the machine showing the rotative head.

Fig. 6 is a vertical section through one of the cutters and its actuating mechanism, the particular cutter illustrated being one of those designed to act in line with the axis of the rock cut, these cutters being termed hereinafter for the sake of brevity straight cutters.

Fig. 7 is a vertical section through the valve mechanism and some of the adjoining parts of one of the two straight cutters at the'center of the series of six, which operate side by side.

Figs. 8 to 15 inclusive, are transverse sec-- tions through the valve mechanism illustrated in Fig. 7, the sections bemg taken upon the lines appearing in Fig. 7 with Specification of Letters Patent.

Patented Feb. 1'7, 1920.

Serial No. 789.600.

numerals corresponding to those of the sectional views. Fig. 16 is a bottom view of the'valve casmg shown in Fig. 7 and other views.

Fig. 17 is a vertical transverse section through the cutter guides upon the irregular line 17 appearing upon Fig. 6.

Fig. 18 is a vertical sectional view of a tappet vent valve shown in Figs. 6 and 7.

Figs. 19 and 20 are horizontal sectional views through the tappet valve upon the lmes 19 and 20 of Fig. 18.

Fig. 21 is a plan view of the throttle valve bushing.

Fig. 22 is a horizontal sectional view of the throttle valve bushing showing the lower opening through the bushing, the upper opening being shown in Fig. 21.

Fig. is a sectional view of a gravity vent valve.

Fig. 2a is a sectional view of the vent valve upon the line 24L of Fig. 23.

Fig. 25 is a sectional view of a pressure reducing valve forming part of the apparatus.

Fig. 26 is a detail view of an air motor and gearing which rotates the cutting head.

In the foregoing description of the drawings and in the following descriptive matter I frequently define the position of the various parts by reference to their position as illustrated. It will be obvious, however, that the various parts of the rotative head are invested with the rotation thereof, and that the terms above, below, etc., are used merely for convenience in describing the mechanism in the position illustrated.

In its general construction the apparatus comprises side members 102 and 103, each composed of two plates, the side members being mounted upon and connected by trucks 10% and 105. Weights 106 at the rear serve to counterbalance the mechanism mounted on the part of the apparatus which projects forward beyond the fore truck 10%. Pneumatic cylinders 107 supplied with compressed air through the pipes 108 are used to advance the machine as the rock cutting progresses. the cylinders 107 carry a cross brace consisting of a central reversely threaded part 110 engaging end parts 111, which latter are slidably mounted in the ends of the plungers 109. At their outer ends the mem- The plungers 109 operating in 111 forms an abutment against which the plungers 109' act toqadvance the apparatus as the rock-cutting proceeds. The e nt1re apparatus rides upon wheels 260 runmng upon rai -ls 112 laidup-on the: bottomof the cut,

the rails being advanced from time to time to .keep pace with the advance. of the apparatus.

Therockccutting part of the apparatus comprises; arevoluble headdesignated generally by the numeral 113 upon Figs. 1 tot. The revolublehead rotates upon a'stationary axis-114 mounted at'its endsupon the :forward end of themain body of the apparatus.

The: revoluble head 113 carries aplurality of radiating cutters arranged in several series or banks. In the. present instance I-have shown two series of cutters designated generally by the numeral 115 .designed'to reciprocate in lines normal to the axis of'the revolublehead, and two series of cutters designated generally by the numeral 116 designed to reciprocate in line inclined to the revoluble head of the apparatus. For-the sake of brevity I will herein term the two series of cutters as 'cornercutters and angle cutters, the latter being designed to form inclinedi corner continuations of the cut made by the straight cutters. It will be-apparent that as the head rotates in the direction-indicated by the arrows in Fig. 1, the reciprocating cutters will form a cut or tunnel having a substantiallyv semi-cylindrical face corresponding to the forward part of the cir'cular path of movement of the cutting indicated in Fig. 1, and that, due to the actionof the corner cutters in conjunction with the straight cutters the cross sectional form ofthe rock out will be as indicated in Figs. 3 and 4, wherein the outer shaded area 117 represents the rock through which-the cut is made.

Power foroperating the rotating head and cutters carried thereby is supplied in theform' ofcompressed air which is con.- ducted to the forward part of the machine through-a valved pipe 100which connects with a conduit'101, the latterbeing flattened at its-forward end as indicated in Fig. 2 for the purpose of compactness. The forward end "of the conduit 101 appears at'the right hand 'of Figs. 3 and 4, the latter view showing the conduit'in section.

The stationary shaft 114 upon which the rotating-head is mounted is screw-threaded into a-supporting block 118 carried'by the side plates 102 of the apparatus. At its opposite end the shaft 114 rests in the supporting block 119 carried by the side plates 103. The upper half 119 of the supporting block 119 is removably held in placeby bolts 120 in order, tofacilitate assemblage. The end of the shaft 114 adjacent the compressed air conduit 101 is bored out centrally to form an axial chamber 121 which opens into a chamber 122 in the block 118, which latter chamber communicates with the compressed air ductin the'conduit" 101, thus afiording a path for compressed air from the pipe 100 to the chamber 121 inthe aint-erior .ofthe shaft .114. 'Thecentral part .ofithe revolving head 113 COI1SlStSfOfi2L casingdesignated generallynby .the. numeral 123, this casing being substanti ally square in longitudinal. vertical section, that .is,. a vertical section longitudi nal of the apparatus-asran entirety.

The central casing 123 is divided-into three partsby partitions'124and 125 forming end chambers'126' and 127, whichare wholly inclosed for the. purpose I of 1 retaining airunder different degrees of pressure. The central compartment 128is open upon two opposite sides, as appears in Fig. 4, and inclosed upon :the' other two sides,..as shown in Fig. 5.

A- worm wheel. 261 is secured to-thecentral part of the. shaft 114 within thespace 128.

by means of two usbolts 129as clearlyshown in Figs. ,4,.and 5 and '26, and it'is through motor propelled gearing carried by the rotative head .and acting upon the stationary worm wheel 261, thatsthe head is" given its rotative movement. Motive power for rotating the head 113 is preferably supplied by an airmotor'130 'mountedupon therotative head, as indicated in Fig. 2. The main shaft 131 of the motor'is supported at one end in thecylinder castings of two of the corner cutters, as indicated in Figs. 3 and 4, and at the other end ina plate 263 shown in Fig. 2 secured to 'the opposite side of the corner cylindercastings. Upon the motor shaft 131, as shown in Fig. 4, and in detail in Fig. 26, *there is mounted a pinion 132 which meshes with the spur wheel'133 mounted upon ashaft-134 carried in bearings 135 secured to the central casing 123 of the rotative head, as shown in Fig. 4. A

worm thread 136 ismounted orformed upon the shaft 134' and meshes with "the worm wheel 261. Compressed air may be supplied to the airmotor 130 from the cham'berx126, or from anyof'the compressedair'ducts in the rotative head.

It will=be apparent from the foregoing that as'the worm wheel 261*isstationary and meshes with themotor driven worm 136 carried by the rotative head eflicientmeans are provided by rotation of the worm for-imparting rotative movement to-the main head 113. In order to adjust the speed of the rotative head 113 to the rate desired, such gearing as is'necessary may be employed between the shaft 131 of the air motor and the worm 136. In the present instance 1 have shown reduction of the air motor speed by means of the pinion 132 and 133 and further reduction, of course, through the worm thread 136 and worm wheel 128.

Proceeding now to the structure of the cutters and the means for actuating them. The cutters are operated by fluid pressure in the cylinders 141 acting upon the pistons 140, the construction and operation of all of the cutters being the same. At the forward end of each of the cylinders 141 there is an .axially projecting cutter guide 142, in this structure shown, see Fig. 6, as an inte gral part of the cylinder. The cutters 143 take the form of triangular prisms, referably equilateral in cross section and aving three cutting edges that may be used in turn. Mounted upon the outer end of the piston rod 144 of the piston 140 is a cutter holder 145provided upon its outer side with an under-cut groove 146, the sides of which have the same inclination as the sides of the cutters 143.

In assemblage the cutter 143 is slid endwise into the groove146, after which it is secured in position by means of a wedge 147 driven between the base of the cutter and the bottom of the groove 146. As clearly shown in Fig. 5, the cutters 143 project at their ends beyond the cutter holders 145 sufliciently to form a substantially continuous cutting edge.

The outer end of the piston rod 144 is tapered and fits into a tapered recess 148 in the base of the cutter holder 145, the tapered fit of these parts securing them together for service and at the same time facilitating removal or" the cutter holders from the piston rods when necessary for renewal of the cutters or other purpose.

Fitting the interior of the cutter guide 142 is a cutter holder bushing 149 centrally bored to receive and guide the movement of the cutter holder 145. Each cutter holder is provided with means for preventing its rotation in the cutter holder bushing, this means in the form of construction illustrated consisting or" a longitudinal groove 150 in the side of the cutter holder engaged by a block or a key 151 secured to the cutter guide and cutter holder bushing by means of a bolt 152.

The cutter holder bushing 149 is formed with a closed inner end formed with a notch 153. A screw plug 154 threaded into the cutter guide engages the notch 153 in such manner as to securely hold the cutter holder bushing in place. It will be observed that the screw plug 154 inclines inwardly toward the axis of the cylinder and cutter holder bushing and at its inner end abuts against the side of the notch 153 which is perpendicular to the axis of the screw plug. By

this means a single screw plug is effective to hold the cutter holder bushing in place and the screw plug is easily accessible for assemblage or removal from the outer face of the cutter. An opening 155 is formed through the side of the cutter guide 142, said opening being closed by a removable screw plug 156.

A registering opening 157 is formed through the side of the cutter holder bushing opposite the opening 155 in the cutter guide, the opening 15'? extending outward beyond the solid base of the cutter holder bushing 149, and inward to theouter head 265 of the cutter cylinder 141.

When it is necessary to remove one or" the cutter holders from its piston red the screw plug 156 is removed and a bar or block in serted through the openings 155 and 157 with its end projecting over the solid base of the cutter holding bushing 149. Then by manually operated means hereinafter to be described, the piston 140, together with the connected cutter holder, is given an inward reciprocation thereby bringing the inner surface of the cutter holder 145 into forcible contact with the inserted bar or block. The outward blow thus imposed upon the cutter head drives it 011' from the piston rod. This arrangement affords convenient and simple power operated means for removing the cut ter holders from the piston rods upon which they are mounted.

From the foregoing description it will be apparent that in case it becomes necessary to renew acutter this object may be accomplished in any one of several ways. Any cutter may be released by simply driving the wedge 14'? out or" its seat beneath the cut ter, thereby releasing the cutter and permitting the cutter to be turned to present a new cutting edge or a new cutter to be inserted; or the cutter holder, together with its cutter, may be removed from the piston rod by inserting a block through the openings 155 and 157 and imparting an inward movement to the cutter holder and piston upon which it is mounted, or if desired, the screw plug 154 may be removed and a complete unit consisting of the cutter holder bushing. cutter holder and cutter may be removed after the cutter holder has been loosened from the end of the piston rod as above described.

The valve mechanism for operating and controlling the cutters is shown in enlarged vertical longitudinal section in Fig. 7. Generally speaking the valve mechanism consists of two parts more or less distinct in structure. but coiiperating in their functions. The first part of the valve mechanism is that whereby admission and exhaust of compressed air to the outer cylinder 141 is controlled and the second part comprises pneumatically operated mechanism r'or automatically adjusting the power supplied to each cutter in proportion to the'resistance encountered thereby. Owing to the -inequality-of the material in which the apparatus maybe used it is necessary to provide means whereby the power supplied .to any individual cutter or cutters which happen to encounter soft material will be-reduced,

wvhile a full supply of power will be maintained to operate those'of the cutters which encounter harder and more-resistant material. The provision of automatically acone of the cutters.

As above indicated, compressed fluid, preferably air, is admitted to the axial bore 121 of the stationary shaft 114 of the rotative head, the arrangement of this part of the mechanism being clearly shown in Figs. 4, 5, and 6. i Radiating from the center bore 121 of the main shaft 114: are a series of radial openings 160 extending from the radial bore 121 to the exterior-0f the shaft 114; and opening into an annular groove'267 upon the exterior of shaft 111. Fixed to the interior of the central casing 123 of the rotative head opposite the axial bore 121 in the shaft 114: is a bushing 161, which bushing is provided with radial openings 162, opening nto an annular groove 268 upon the interior of the bushing, the grooves 267 and 268 being in registry to establish continuous communication Y between radial openings 160 and 162. Angular gaskets 163 form a fluid. tight joint between the rotative head and the shaft 111; The radial open in' 's 160, 162 together with annular grooves 26 and 268 form'ducts for the passage of compressed air from the bore 121 to the chamber'126 at one end of the rotative head. In the interior of the wall 123 of the central casing 123 of the rotative head 113 is a duct 165, as elearly'shown in Figs. 6 and 7. This duct extends across the face of the head in order to afford communication-with all of the series of straight cutters. The arrangement for both of the banks of straight cutters is the same. The duct'165 is connectedwith the chamber "126 by a duct 2 shown in 'Figs. 6 and 7. Extendingfrom the duct 165 opposite each of the cutters is a duct 2 which extendsupwa'rdly, in the po sition of the parts shown in Fig. 7, from the duct 165 and then extends at an angle to the outer surface of the side/123 of the central casing 123 of the rotative -head.

7 As shown most clearlyin Fig. 6, thetool cylinder casting comprises the toolcylinder proper containing thetool piston -14:0-,the

outwardly extending-cutter guide 142 and a flange 166- which lies a ainst the :outer surface of the side 123 of the central casing 123 of the rotative head. The valve mechanism for the operation of the cutters is contained in a valve casing designated generally by the numeral 167 lhis-valvecasing fitsin the angle formedbetween the side of uthe cylinder 141 and its end Efiange' 166, the same being-shown in longitudinalsection in Figs. 6 and 7. The Valve-casing 167 takes diflerent cross sectional: forms at different ivducts which are formed in the wallsthereof.

The different cross sectional forms ofthe valve casing are illustrated in Figs. Ste 15,

reference to which-viewsin connection with the longitudinal SECtlOIlS 6 and :7 W111 be-had in the explanation of the valvemec'hanism.

The operation of :the -valve-mechanism centers about two cylinders, the control cylinder 168 at the upperpartthereof, and a differential cylinder 169 in: .the' lower :part of the valve casing, the cylinders "168 and 169 being desi nated by :those numerals upon Fig. 6. The cylinder 1*68 is-provided at itsouter end with a removable head 170 secured in place by bolts"171. The cylinder 169 is closed by the flange 1660f the cutting cylinder when the valve casing is placed in position, as shown; in Fig.6. The bore of the differentialcylinder-169 is formed in a cylinder bushing 172 fitted to a cylindrical opening in theunain body of the-valvecasing 167, the-large bore 169 of the difierential cylinder being at theleft andthe small bore- 169 beingat--the .right as viewed in Figs. 6 and 7. Fitted: to and operating in the differential cylinder is a differential piston having a large head 172 -operating in the large part of the cylinder and a small head 172 operating inthe small-part'o-f -the difierential cylinder. The -diifer'entia'l piston 17 2 is =hollow'and so formed as to divide-the space within the differential cylinder= into three chambers-,( 1) a high pressure chamher 173 in the interiorof the small part of the hollow piston; an exhaust chamber 174 between thelarge and s'mallparts "of the piston and surrounding the stem which'con- V nects the large. andsn'iall parts; and the space 175 between the'lar eart" of the piston and the-end of-the'cy in erp-fThe small part of the hollow cylinder. is open at its end and hence the high pressure-space in the-interior 'of-thesmallpart of the pistonis continuous with'the-space inside of the small part of a the cylinder when' the piston is moved towardthe large end ofth'e cylinder, in which 'positionthe high pressure chamber includes not only the interior of the small part of the piston, but the adjoining space in the small part of the cylinder wherein it moves.

A duct 22 through the flange 166 of the tool cylinder 141 re isters with the duct 2 in the side 123 of the central casing of the rotative head and aflords communication with a passage 2'. formed in the adjoining part of the valve casing 167. A cylindrical opening 179 extends from the end of the cylinder 168 and is connected by a short cross passage 2 with the duct 2 in the valve casting. Fitted within the cylindrical opening 179 is a throttle valve bushing 180, which is slotted in its opposite sides in registry with the short cross passage 2, the slots or parts in the opposite sides of the throttle valve bushing being designated 2 and 2 The piston rod 182 of the central piston 183 operates as a throttle valve in the throttle bushing 180. Registering with the lower port 2 of the throttle valve is a duct 2 g through the valve casing and leading to an annular groove 2 extending around the exterior of the differential cylinder bushing 172. Upon the interior of the differential cylinder bushing 172, opposite the annular groove 2 is an annular groove 2, and the grooves 2 and 2 are connected by a plurality of radial passages 2 Extending through the small part of the differential piston 50 are a series of radial passages 2 which in all positions of the differential piston register with the annular groove 2 upon the interior of the differential valve bushing 172.

In the body of the valve casing and surrounding the differential valve bushing is a duct 1 of the general form shown in Figs. 7 and 8. The duct 1 communicates with radial ducts 1 extending through the diflerential valve bushing 172, which ducts 1" open into an annular groove 1 upon the interior of the diflerential valve bushing 172. The duct 1 in the valve casing communicates with ducts 1 in the wall of the cylinder 141, the ducts 1 opening into said cylinder and forming the high pressure admission ports. The extent of movement of the difi'erential cylinder valve is such that when the valve is moved to the left from the position illustrated in Fig. 7, the groove 1 will be uncovered, thus opening communication between the interior of the small part of the differential piston and the tool cylinder 141, and when the differential piston is so moved to the left air under pressure will be admitted from the high pressure chamber 126 through the passages 2, 165, 2", 22, 2?, 2, 2 2 ,2, 2 the annular groove 2", the radial passages 2 the annular groove 2 the radial passages 2 to the interior of the small part of the differential piston, thence to the groove 1,

through the openings 1 to the space 1, and through the ports 1 to the tool cylinder. It will be noted that the high pressure fluid in the course of its passage to the interior of the tool cylinder first passes through the interior of the small part of the differential piston, thence around the end thereof through the openings 1 which communicate with the admission ports 1.

The differential piston 172 is constantly impelled to the left from the position illustrated in Fig. 7 by the high pressure fluid constantly maintained upon the right side I of, that is, within, the small part of the differential piston, such high pressure being constantly maintained, as above indicated, by the fact that the openings 2 in the small part of the differential piston register in all positions with the groove 2 in the differential cylinder bushing 172.

For moving the differential piston to the position illustrated in Fig. 7, the following means are provided: A small duct 3 leads transversely from the high pressure fluid passage 2", as illustrated in Figs. 7 and 9, and is continued in a longitudinal direction, as indicated by the part designated by the numeral 8 shown in Figs. 7 and 9, and is thence continued downwardly and opens into the large end of the differential cylinder, as indicated by the numeral 3 in Figs. 7 and 10. The passage ,of high pressure fluid through the duct 33 3 to the large end of the differential cylinder is controlled by a needle valve 186 which cotiperates with a seat formed at the end of the passage 3. The stem of the needle valve 186 is threaded, for adjustability, into the side of the valve casing opposite the opening of the passage 3, as indicated in Fig. 9, and a locknut 187 is provided for the purpose of holdingthe needle valve in adjustment.

Also opening into the large end of the differential cylinder is a vent duct 3 clearly shown in Figs. 7 and 11, which extends longitudinally a short distance where it connects with a vertical passage 8 which in turn connects with a valved passage 33, which extends to a cross duct 3 The cross duct 8 extends across the entire series of straight cutters, and the vent passages of each of the straight cutters of the series open into it. At some convenient point a passage 189 extends upwardly from the passage 3 to the top edge of the base flange 166 of the tool cylinder 141, this passage being shown in Fig. 5 as at. the center of the flange. Connecting with the passage 189 is a pipe 198 which extends upwardly and outwardly, as indicated in Fig. 6, and at its upper end has a part 198 extending substantially parallel to the axis of the rotative head, as indicated in Figs. 1 and 3.

Connected to the end of the pipe 198 as shown in detail in Fig. 23, by a screw collar,

is a conical valve plug 194 upon which is tical position illustrated, regardless of the position assumed by the rotative head in its movement. The conical valve plug 194 has a central axial recess 200connected to the exterior of the plug by a slot 201. Thegravity valve 191 is provided adjacent its upper apex with a conical opening in' which the valve plug 194 isseated, and communicating with the conical opening in the v gravity valve 191 is a chamber 192 extending through substantially a semi circle and forming an-oft'set from the conical opening.

The chamber 192 'connnunicates through an opening 190 with the atmosphere. The gravity'valve 191 is'held to'its'seat upon the conicalplug- 194'by means of a spring 195 abutting at one end againsta washer 196 held upon the stem of the conical plug 194 by a pin 197. I

'From the foregoing it will be-appa-rent that the interior 200 of'the conical plug 194 will be in communication with the atmosphere during half of each 'revolution'of the rotative head 113 this by reason ofthe fact that the'con'ical plug 194 is fixed to and rotates with the head, while the gravity valve turns upon the plug 194 by' reason'of the fact that it is always maintained in a vertical position by the'force of gravity. As illustrated in Figs. 23 and 24, the-gravity valve is in its middle position with the slot 201 of the valve plug closed'and midway between the ends of the'cha'mber 192. This is the position occupied by the gravity valve relative to the valve plug governing the series of cutters occupying a rearward horiz'ontal position, as illustrated in- Fig. 1, the

' position of the rearward horizontal cutters being designated by the letter A. It will be'evident that when the rearward straight cutters A illustrated in Fig. 1 have turned through a quarter of a revolution bring ing them to an upward vertical position, the gravity valve 191 will open the vent, which ends in the conicalplug 194, to the atmosphere and that the vent will remain open until the head has turned'through a semirevolution bringing the series of straight cutters referred to to a vertically downward position, and that at that point the gravity valve 191 will again close the vent and malntain it closed while the straight cutters of theserles referred to are moving through thesemi-revolution in which they are not opposed-t0 the face of the rock cut. All of the" cutters of the apparatus are similarly provided with gravity valves, whereby'vents corresponding to the one'a'bove described in detail are maintained closed during the idle A spring I 209. SEIQG'CODDGCtS"Wltll a chamber 210 above the semi-revolution of the cutters, and are main clearly in Figs. 7 and 11 to 14 inclusive.

The hand valve 205 is capable of three functions. lVhen turned to the positionshown in Fig. 7 a passage 3 through the plug of the hand valve maintains the continuity of the vent passage. When the'valve is turned" 90 degrees clockwise from the position shown in Fig. 7 the ventpassage is closed at the hand valve, the large end of thedifferential cylinder at such time having'no communication'either with the atmosphere or with thela part'of the vent passage beyond the hand va ve.

shown in F ig.-7 the large end of the dif- 'difierential cylinder-so long as the hand -valve is maintained in the last described position.

The vent passage is further controlled at a point between the parts thereof designated 3 and '3 by means of a tappet valve 207, illustrated in Fig. 7 and in detail in Figs.

1 18, 19 and 20. The conical seat of the tappet valve is formed in a bushing 208 set in a recessin' the lower side of the valve'casing and the "conical valve 207 normally maintained aipolr-its seat by'ineans of a spiral The part 3 of the vent pasvalve seat and the part 8 of the vent passage connects with a space 211 below the valve seat. Seated in' a bushing 212, which is fitted 'toa recess in the wall of the tool cylinder 141, is a ball tappet 213 held in place bythe restricted lower end of the.

opening in bushing'212. A pin 214 is slida'b'lyseated in a plug 215 which closes the 140; It will be apparent that upon its backw'ard stroke the tool piston 140 will contact w1th the tappet "ball 213' andpush' it outward,which outward movement will-be communicated to the pin 214 and from the pin 'to the tappet valve 207, thereby 'ra isingthe latter from'its s'eat'and opening communication'between' the parts 3: and 3" of the vent passage. Upon the forward stroke of The hand vent valve is provided in its outer surfacewith'a groove 206 whereby when the vent valve'is turned about l5 degrces counterclockwise from the position 

